The present invention relates to a method of bending a glass sheet in more than one dimension. More particularly, the invention relates to a method of bending a heated glass sheet by roll forming such that different bending profiles may be formed in portions of the same glass sheet.
Glass sheets suitable for, for example, vehicle windows are conventionally heated to temperature suitable for shaping and are conveyed therefrom by a conveying system into a first roll shaping zone, where they are conveyed between upper and lower sets of rotating shaping rolls having a first shaping configuration. Each set of upper and lower shaping rolls have complementary shapes so as to allow a glass sheet to pass therebetween, and to take the cumulative shape of the entire set of upper and lower shaping rolls, while still being susceptible to further alterations in shape. In general, shaping in the first roll shaping zone is preferably transverse to the direction of travel of the glass sheet.
It is advantageous to transport the heated glass sheets through the roll shaping zone at as high a speed as practicable to reduce cycle time, and to maintain the glass sheet at a temperature sufficient to allow additional shaping in, for example, an inclined second roll shaping zone. Such additional glass shaping is preferably accomplished by the glass sheet being transported from the horizontal first roll shaping zone, up the slope of the inclined second roll shaping zone which preferably includes, upper and lower shaping rolls having a shaping configuration substantially similar to the first shaping configuration of the horizontal roll shaping zone. Shaping in the inclined second roll shaping zone is, primarily, longitudinal, that is, generally parallel to the direction of travel of the glass sheet.
Bending a heated glass sheet by roll forming is known in the patent literature, for example:
U.S. Pat. No. 3,545,951 describes a plurality of arcuately curved rods mounted for rotation each about its own chordal axis. The axes are said to be coplanar, parallel and spaced, and the rods are said to be interconnected for pivoting in unison each about its own axis, from a first position, wherein they are said to be coplanar in a common plane through all axes, to a second position wherein they are said to conjointly define a curved surface whose curvature is variable in dependence upon the angle of rotation of the rods. Sheets said to be in bendable form are moved onto the rods in the first position. The rods are then pivoted to the second position and shaping means complementary to the curved surface defined by the rods are pressed down onto the sheet to conform it to the rods, while the sheet moves continuously, and after shaping, passes to a cooling and tempering chamber or other processing procedure.
U.S. Pat. No. 4,054,037 describes a sheet to be curved, such as glass at a softening temperature, being advanced on a fixed curved bed formed by a series of curved rods having different angles of inclination to form an ascending convex bed with an increasing curvature profile. The sheet is thus gradually raised and simultaneously curved by sagging of the edges thereof. The curved rods are said to have aligned end sections mounted in the same horizontal plane and the inclinations progressively increase. The bed is followed by a bed of constant curvature profile formed by curved rods having the same inclination. Means are said to be provided for independently adjusting the inclination of each rod. Particular ranges of spacing and rate of advance are said to be given.
U.S. Pat. No. 4,123,246 describes shaped solid members such as successive rotating shaping rolls of predetermined contour of a uniform cylindrical or curved configuration which engage a heat-softened glass sheet along an arcuate longitudinal path of substantially constant radius of curvature along forming and quenching conveyors to impart a desired longitudinal component of curvature to the glass and to convey the shaped glass past cool blasts that harden the glass surfaces. The arcuate path is said to be arranged in such a manner that its upward slope at its downstream end is said to be limited to one at which glass sheets move forward toward the cooling conveyor without slipping. A set of at least three special quench rolls forms an upwardly sloped transition conveyor section of constant maximum slope that replaces the downstream portion of the arcuate path where the upward slope would increase to a slope where slippage would take place. The special transition quench rolls are located downstream of the location where blasts of tempering fluid applied at the quenching section have hardened the major glass sheet surfaces sufficiently to, desirably, avoid their distortion by engagement with the rotating special transition quench rolls.
U.S. Pat. No. 4,292,065 describes a method and apparatus for bending sheets in the plastic state, such as sheets of glass at their softening temperature in two directions. The apparatus comprises a first bed of arcuate rods which can be positioned to impart a transverse curvature to the sheet and a second bed of arcuate rods which can be positioned to impart a longitudinal curvature to the sheet. Advantageously, the bending is performed in a heated enclosure at a temperature at least equal to that at which the sheet is later tempered.
U.S. Pat. No. 4,556,406 describes a roll forming apparatus for shaping heat-softened glass sheets into a configuration having a longitudinal radius of curvature that varies in a direction transverse to the glass sheet. The first end of a first traversing cylindrical roll, and a first and second series of longitudinally spaced and transversely extending forming rolls is mounted so that a longitudinal edge of the glass sheet is positioned along a first continuous arcuate path defining a first longitudinal radius of curvature and a second end of each roll is mounted such that an opposing longitudinal edge of the glass sheet is positioned along a second continuous arcuate path defining a second longitudinal radius of curvature. The first and second longitudinal radii are said not to be equal so that a set of upper forming rolls overlays the second series of forming rolls and have a complementary overlying shape.
U.S. Pat. No. 4,820,327 describes bending a heated glass plate by moving it over a bed of rollers defining a path curved along the direction of movement of the glass plate so as to define an upwardly facing concavity. The glass plate moves with a speed of at least 10 cm/sec and is curved by the bed without contact from above. The glass plate is subsequently tempered.
U.S. Pat. No. 5,395,415 describes a method and apparatus for precisely shaping heated glass sheets as the sheets advance along a bed of conveyor rolls. The conveyor rolls comprise a core member having axially aligned opposite sections and an arcuately curved central portion, with a flexible sleeve surrounding the core member. The core members are pivotable in unison between a first position where the curved portions lie in a common plane for conveying the flat sheets and a second, lowered position such that the curved portions define the shape to which the sheets are to be deformed. Vertically reciprocal top surface press units are mounted above the path of the glass sheets. The press units include curved stationary mandrels having freely rotatable flexible sleeves thereon. The configurations of the mandrels are said to be such that in operative position, the mid-portion of the first press unit is slightly closer to the path defined by the conveyor rolls than the edge portions, and the edge portions of the second mandrel are said to be slightly closer to the path than the mid-portion.
Notwithstanding the previously known roll forming methods, it would be advantageous to provide an apparatus and a method that would allow forming non-uniform shapes in a single sheet of glass, for example, forming different shapes of the leading and trailing edges of a glass sheet, by a roll forming process that meets the requirements of high-volume glass manufacturing.